Views as User Controls or Windows

I am new to this and as such probably being an idiot...that said, do I want my Views to be UC's or Windows? I'm guessing it depends on my usage scenario.

I have a main view that has "buttons" on it for different actions, e.g. CreateThis or ModifyThat. When the user clicks on one of these "buttons" I want to show an appropriate View in a Dialog type scenario. This SEEMS like it would lend
itself to being a Window however I'm not sure how the Window Manager factors into this.

Also, when I did Winforms development I made all my "views" UC's that I would embedd in one reusable Window so that they were more flexible, is that something that apply's here?

I have 1 window for the shell and the rest of my "windows" are UCs that will be dropped onto a generated window with the use of the WindowManager, simple and complex in one package. ShowDialog creates the window and from there is populated with
that of the UC from the viewmodel in question.

I am sure everyone else has a different opinion for that particular use case but for me "it just works"...